How to make a sandbag wall?
Final result:
You can use Array modifiers along with simple Sculpt to achieve similar result. It's a bit more of manual work but it's pretty simple and rewarding at the end.

Mesh:
You will need something similar to mesh from the screenshot. The goal is to have brick-like array. Top part is duplicate of the bottom part, cut in a half and manually placed.

Modifiers:
Here you will need at least two Array modifiers (width and height) or three if you want to have some multiple rows.
One of them (width, in this case X axis) should have checked Merge to connect top part of the mesh.

Sculpt:
When you make the wall with desired size it's time to duplicate it to another layer. To have some backup.
After it, apply modifiers from top to bottom. It's good idea to go to Edit Mode, Select All and Remove Doubles just in case.
You can add Mulitresolution modifier (I've added it with Subdivision 1) but it can stay low poly.
Go to Sculpt Mode, turn off Symmetry Lock X, choose Grab Brush and start tweaking the mesh. Remember to change Brush size/strength once in a while to give it more detailed look.
You can do this with mouse, no need for tablet to do this.

Blend file:
First layer contain mesh with Array modifiers, second one is the final mesh.